Rendering artifacts in the macOS UI on macOS Tahoe 26.x

It doesn't look like the traditional hardware rendering issues, but it also doesn't really look the usual software rendering bugs either. My first instinct is a software issue though as it matches more closely than hardware glitches, but both the Apple M-series hardware is a lot different as is Tahoe.

Testing in Safe Mode is the easiest test to determine if some third party software could be causing the problem, but unfortunately Safe Mode isn't as fool proof of a test these days with more recent versions of macOS. The better test would be to test the system with a clean install of macOS without any third party software installed & without having restored anything from a backup. This is the only way to completely eliminate third party software from causing a problem.

There are several ways to do this depending on how much Free storage space your system has (install macOS to a new APFS volume if the system has at least 80GB+ Free space), whether you have a spare external SSD to temporarily use for installing & booting macOS, or just "Erase All Content & Settings" to wipe all modifications & data from the system leaving it with a "clean" OS. FYI, the only place to easily view the actual Free storage space is in Disk Utility.....ignore the "Available" storage value shown everywhere in macOS since it is not synonymous with Free.

To test an older version of macOS to compare a clean install of Sequoia and Tahoe to see if it is a Tahoe issue exclusively, then you would need to create a bootable macOS USB installer in order to install a specific version of macOS. Even a recent version of Sequoia or Sonoma may include some aspects of Tahoe in the more recent patch levels so comparing multiple versions of macOS point releases is needed to be sure of an OS bug, or hardware issue.

You can try running the Apple Diagnostics, but it is very doubtful it report any problems. The Apple Diagnostics (even the service diagnostics) have degraded over the years and no longer perform any in-depth testing needed to identify problems. The diagnostics just look to make sure various hardware components are able to be seen & identified.....sometimes a very basic test may occur where only the most severe hardware issue may possibly cause a problem. While booting & running the diagnostics make sure to watch the laptop's screen the whole time to see if you notice any graphical glitches....if so, then it most likely indicates a hardware issue. It still doesn't hurt to run the diagnostics just on the off chance it reveals a problem.

Did this machine experience the same issues when running macOS 15 Sequoia ?

If no

I suspect this could be a macOS 26.2 Tahoe issue

In which case, hold off the Panic Button until the Tahoe 26.3 is commercially released sometime in early 2026

mercurial81 wrote:

Thanks for the answers guys. I downgraded to Sequoia and all looks perfect, no graphic issues at all

Thank you for the followup

This must be great news for you

These action you have taken, downgrading back to Sequoia, seems to semi confirm there is still more work to done on macOS 26 Tahoe

mercurial81 wrote:

Does this pattern point more toward a macOS rendering bug vs. a hardware/GPU issue, and what diagnostics should I run before contacting Apple (sysdiagnose, Apple Diagnostics, etc.)?

This looks like a hardware fault. Tahoe definitely has rendering bugs, but they don't look like that.

From what I have read elsewhere

It could be Apple's dependence on the newer Metal 4 that could be still in a refinement mode sort of speak

Generally on new version of macOS

Somewhere around the point 3 update do things start to come together

What external display and how is it connected to the MBP..?

(make, size, model, type of cable and adapter if used)

Does it happen on the MBP display when the external display is disconnected..?

(test without that external display and/or test a different external display)

Yes I understand that it shows up on both the internal and external displays.

To answer to your third question:

The Apple Diagnostic Test has never been ably to full test the GPU hardware.

Again:

What external display and how is it connected to the MBP..?

(make, size, model, type of cable and adapter if used)

Does it happen on the MBP display when the external display is disconnected..?

(test without that external display and/or test a different external display)

mercurial81 wrote:

1. BENQRD280UA - 28", connected via USB-C

2. Yes, it happens with or without the display. I see the issue on both the external display and the MBP screen, whether the MBP is connected to or disconnected from the external display.

Thank you.

Take the MBP to your local Apple Authorizes Service Provider for evaluation.

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mercurial81 wrote:

Is anyone else seeing similar UI artifacts1.  on Tahoe 26.x on Apple Silicon?

I'm not. Not on an M3 iMac or an M1 MBA.